About five species: Bhutan, China, India, Myanmar, Nepal, Thailand, Vietnam; three species (one endemic) in China.

The relationships of Luculia have not been clear until recently, when molecular studies (e.g., Bremer et al., Syst. Biol. 48: 413-435. 1999) found it to be basal in the Rubiaceae. Additional references regarding Luculia’s biology and classification, not listed here, were cited by Rydin et al. (Pl. Syst. Evol. 278: 101-120. 2009).

The treatment here summarizes the existing taxonomy, as a basis for future work; it seems possible that there are only two species in China, but evaluation of this is beyond the scope of this study and the available specimens. Hutchinson (in Sargent, Pl. Wilson. 3: 408. 1916) gave taxonomic significance at the species level to the presence vs. absence of "striking flap-like processes upon and continuous between the lobes of the corolla" for separating species of Luculia; these structures have not been much studied or detailed by other authors.